Method of forming a composite article by metal spraying

Abstract

The method of making a composite article of different metal portions by spraying molten metal on the surface of a solid metal member that has been cleaned and preheated in a controlled atmosphere at low pressure. The molten metal is sprayed on the surface of the solid metal member, preferably by plasma jet spraying. It is rapidly solidified to be adherent to the surface of the solid metal member to form a composite preform. The composite preform is cooled at a rate sufficiently low to reduce residual stresses and then hot pressed to eliminate voids in the sprayed metal portion and metallurgically bonded to the surface of the solid member.

What is claimed is: 
     
       1. A method of making a composite metal article by spraying molten metal on the surface of at least one solid metal member, said method comprising the steps of: providing a solid metal member;   facilitating the formation of a metallurgical bond at the interface between the surface of said metal member and metal sprayed thereon by cleaning the surface of said metal member and preheating said metal member in a controlled atmosphere at low pressure;   spraying molten metal onto the surface of said metal member;   rapidly solidifying said molten metal incrementally to form a solid partially porous sprayed metal portion adherent to at least a portion of the surface of said metal member to form a composite preform;   reducing residual stresses at said interface by cooling said preform at a sufficiently low cooling rate; and   hot pressing said preform to substantially eliminate voids in said sprayed metal portion and metallurgically bond said sprayed metal portion to the surface of said metal member.   
     
     
       2. The method of claim 1 wherein said solid metal member is substantially gas impervious, said method including the steps of forming a gas impervious layer on the surface of said partially porous sprayed metal portion and hot isostatic pressing said preform. 
     
     
       3. The method of claim 1 wherein said metal article comprises nickel. 
     
     
       4. The method of claim 3 wherein said metal member is preheated in the range of from about 1500° F. to 1800° F. 
     
     
       5. The method of claim 1 wherein the step of preheating said metal member comprises the step of impinging a high velocity thermal plasma on said metal member. 
     
     
       6. The method of claim 5 wherein the step of cleaning the surface of said metal member is accomplished by forming a direct current arc on the surface of said metal member, the surface of said metal member being the cathode. 
     
     
       7. The method of claim 1 wherein the step of spraying molten metal is accomplished by injecting powdered metal into a plasma directed at said solid metal member. 
     
     
       8. The method of claim 7 wherein said metal comprises nickel. 
     
     
       9. The method of claim 1 including the step of moving said solid metal member with respect to means for spraying said molten metal while spraying said molten metal onto the surface of said metal member. 
     
     
       10. The method of claim 1 wherein said solid metal article comprises a directionally solidified metal member. 
     
     
       11. The method of claim 1 wherein said solid metal article comprises a single crystal metal member. 
     
     
       12. The method of claim 1 including the step of changing parameters associated with the step of spraying said molten metal to change the grain size of said sprayed metal portion. 
     
     
       13. A method of making a composite metal article of near theoretical density comprised of at least one single crystal member metallurgically bonded to a fine grained portion, said method comprising the steps of: providing at least one gas impervious solid metal member, said solid metal member being a single crystal;   facilitating the formation of a metallurgical bond between said fine grained portion and said single crystal member by cleaning the surface of said single crystal member where it is disposed to contact said fine grained portion, said cleaning step being in a controlled atmosphere at low pressure;   preheating said single crystal member in a controlled atmosphere at low pressure;   spraying molten metal within a high velocity thermal plasma onto the surface of said single crystal member;   rapidly solidifying said molten metal incrementally to form a fine-grained solid partially porous sprayed metal portion adherent to at least a portion of said single crystal solid metal member to form a composite preform;   forming a gas impervious layer on the surface of said partially porous sprayed metal portion;   reducing residual stresses in said preform by cooling said composite preform at a sufficiently low cooling rate; and   hot isostatically pressing said composite preform to substantially eliminate voids in said sprayed metal portion and metallurgically bond said sprayed metal portion to said single crystal member.   
     
     
       14. A method of making a composite metal article by spraying molten metal into at least one solid metal member, said method comprising the steps of: providing a solid, gas impervious metal member, said member containing a cavity therein;   facilitating the formation of a metallurgical bond at the interface between the surface of said cavity and metal sprayed thereon by cleaning the surface of said cavity and preheating said metal member in a controlled atmosphere at low pressure;   spraying molten metal into said cavity;   rapidly solidifying said molten metal incrementally within said cavity to form a solid partially porous sprayed metal portion, said metal portion substantially filling said cavity and being adherent to at least a portion of the surface of said cavity to form a composite preform, with the outermost portion of the solidified metal portion being substantially gas impervious;   reducing residual stresses at said interface by cooling said preform at a sufficiently low cooling rate; and   hot isostatically pressing said preform to substantially eliminate voids in said sprayed metal portion and metallurgical bond said sprayed metal portion to the surface of said cavity.   
     
     
       15. The method of claim 14 wherein said metal article comprises nickel. 
     
     
       16. The method of claim 15 wherein said metal member is preheated in the range of from about 1500° F. to 1800° F. 
     
     
       17. The method of claim 14 wherein the step of preheating said metal member comprises the step of impinging a high velocity thermal plasma on said metal member. 
     
     
       18. The method of claim 17 wherein the step of cleaning the surface of said metal member is accomplished by forming a direct current arc on the surface of said metal member, the surface of said metal member being the cathode. 
     
     
       19. The method of claim 14 wherein the step of spraying molten metal is accomplished by injecting powdered metal into a high velocity thermal plasma directed at said solid metal member. 
     
     
       20. The method of claim 19 wherein said metal comprises nickel. 
     
     
       21. The method of claim 20 including the step of moving said solid metal member with respect to means for spraying said molten metal while spraying said molten metal onto the surface of said metal member. 
     
     
       22. The method of claim 20 including the step of forming said sprayed metal portion with a different grain size in different parts of said sprayed metal portion. 
     
     
       23. A method of making a composite metal article by spraying molten metal into at least one solid metal member, said method comprising the steps of: providing a solid, gas impervious metal member, said member containing a cavity therein;   facilitating the formation of a metallurgical bond at the interface between the surface of said cavity and metal sprayed thereon by cleaning the surface of said cavity and pre-heating said metal member in a controlled atmosphere at low pressure;   injecting metal powder into a high-velocity thermal plasma directed at said cavity to form a spray of molten metal;   spraying molten metal into said cavity;   rapidly solidifying said molten metal incrementally within said cavity to form a solid partially porous sprayed metal portion, said metal portion substantially filling said cavity and being adherent to at least a portion of the surface of said cavity to form a composite preform, with the outermost portion of the solidified metal portion being substantially gas impervious;   reducing residual stresses at said interface by cooling said preform at a sufficiently low cooling rate; and   hot isostatically pressing said preform to substantially eliminate voids in said sprayed metal portion and metallurgical bond said sprayed metal portion to the surface of said cavity.   
     
     
       24. The method of claim 23 wherein said metal article comprises nickel. 
     
     
       25. The method of claim 24 wherein said metal member is preheated in the range of from about 1500° F. to 1800° F. 
     
     
       26. The method of claim 24 wherein the step of preheating said metal member comprises the step of impinging a high-velocity thermal plasma on said metal member. 
     
     
       27. The method of claim 26 wherein the step of cleaning the surface of said metal member is accomplished by forming a direct current arc on the surface of said metal member, the surface of said metal member being the cathode. 
     
     
       28. The method of claim 23 wherein the step of spraying molten metal is accomplished by injecting powdered metal into a high velocity thermal plasma directed at said solid metal member. 
     
     
       29. The method of claim 23 including the step of rotating said solid metal member while spraying said molten metal onto the surface of said metal member.